Driving control system for vehicle

ABSTRACT

A vehicle has a shift mechanism and a position detection device that detects an operation position of the shift mechanism. A transmission is brought to a power transmission state when an operation unit of the shift mechanism is operated to a driving position, and is brought to a power interrupt state when the operation unit is operated to a non-driving position. A driving force limitation process for reducing the driving force of an internal combustion engine is executed when it is determined that the non-driving position has been shifted to the driving position on the basis of the operation position of the operation unit as detected by the position detection device. The driving force limitation process is prohibited when it is determined that the vehicle is traveling and that the operation unit is not operated to any of the operation positions.

The disclosure of Japanese Patent Application No. 2011-280385 filed onDec. 21, 2011 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a driving control system for vehicles.

2. Description of Related Art

Motors such as internal combustion engines and electric motors areinstalled as driving sources, in vehicles such as automobiles. Suchmotors are coupled to wheels through a transmission. The vehicle isprovided with a shift mechanism that allows switching, in response to anoperation by the driver, between a driving position (for instance, aposition such that the vehicle travels forward, or a position such thatthe vehicle travels in reverse) and a non-driving position (forinstance, a parking position or a neutral position).

An operation lever, as an operation unit of the shift mechanism, iscoupled to the abovementioned transmission (specifically, to a shiftfork of the transmission). When the operation lever is operated to adriving position, the transmission is brought to an operation state(power transmission state) in which a driving force is transmitted fromthe motor to the wheels, and when the operation lever is operated to anon-driving position, the transmission is brought to an operation state(power interrupt state) in which transmission of the driving force fromthe motor to the wheels is interrupted.

In vehicles of a related art, wherein driving force is transmitted froma motor to wheels (Japanese Patent Application Publication No.2010-18174 (JP-2010-18174 A)), a driving force limitation process forlimiting the driving force that is outputted by the motor is executedwhen an operation position of a shift mechanism is shifted from anon-driving position to a driving position, in a state that theaccelerator operation member of the vehicle is operated to the on state.In such a device, the driving force that is transmitted from the motorto the wheels is kept small even in a case where the shift mechanism isoperated from a non-driving position to a driving position in a state ofincreased motor output that results from the operation of theaccelerator operation member. As a result, discomfort to the driverresulting from transmission of the driving force can be suppressed, anda decrease in drivability is suppressed.

Shift position sensors for detecting the operation position of theoperation lever are ordinarily mounted in the shift mechanism. Suchshift position sensors are made up of detection units (for instance,switches) that are respectively mounted in the vicinity of eachoperation position of the operation lever, The operation position of theshift mechanism is detected on the basis of output signals of thedetection units.

In such a position detection device, a state is detected in which,although temporarily, the operation lever is not operated to any of theoperation positions, when the operation lever is at intermediatepositions between operation positions in the course of the shiftingoperation of the shift mechanism. In cases where, for instance, theoperation lever is operated slowly, such a state may in some instancesgo on for a comparatively long time, depending on the way in which theoperation lever is operated to the respective operation positions.

When a state is brought about in which the operation lever is notoperated to any of the operation positions upon operation of theoperation lever from a non-driving position to a driving position, theoperation state of the transmission that is coupled to the operationlever is brought to a power transmission state, and the operationposition of the shift mechanism detected by the position detectiondevice is not a driving position. At this time, the vehicle starts as aresult of the actual operation state of the transmission being broughtto the power transmission state, despite the fact that the operationstate of the transmission, as determined on the basis of the detectionresult by the position detection device, is still a power interruptstate. Accordingly, the above-described driving force limitation processis initiated, as a result of which the vehicle may stall and drivabilitydecreases, when the operation position of the operation lever is broughtthereafter to an adequate position and the position detection devicedetects that the operation position of the operation lever is a drivingposition.

In the above-described device, thus, a discrepancy may arise between theactual operation state of the transmission and the operation state ofthe transmission as determined on the basis of the detection result bythe position detection device. Drivability may be impaired on account ofthat discrepancy.

SUMMARY OF THE INVENTION

The invention provides a driving control system for a vehicle thatallows suppressing decreases in drivability through execution of adriving force limitation process with adequate timing.

A driving control system for a vehicle of an aspect of the invention isprovided with: a shift mechanism that is used in a vehicle in which amotor as a driving source is coupled to wheels via a transmission, andthat is configured such that an operation unit coupled to thetransmission is selectively shifted to one operating position of adriving position and a non-driving position; a position detection devicethat detects the operation position of the operation unit on the basisof an output signal of a detection unit that is attached to each of theoperation positions of the operation unit; and a controller thatexecutes a driving force limitation process for limiting a driving forcethat is outputted from the motor, when it is determined that theoperating unit is shifted from the non-driving position to the drivingposition on the basis of the operation position of the operation unit asdetected by the position detection device, in a state that theaccelerator operation member of the vehicle is operated to an on state;wherein the shift mechanism brings the transmission to a powertransmission state in which the driving force from the motor istransmitted to the wheels, when the operation unit is operated to thedriving position, and brings the transmission to a power interrupt statein which transmission of the driving force from the motor to the wheelsis interrupt, when the operation unit is operated to the non-drivingposition; and the controller prohibits the driving force limitationprocess when it is determined that the vehicle is traveling and that theoperation unit is not operated to any of the operation positions on thebasis of a detection result by the position detection device.

The driving control system for a vehicle of an aspect of the inventionallows suppressing decreases in drivability through execution of thedriving force limitation process with adequate timing.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the invention will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic diagram illustrating the schematic configurationof a driving control system for a vehicle according to a specificembodiment of the invention;

FIG. 2A is flowchart illustrating an execution procedure of a drivinglimitation routine;

FIG. 2B is flowchart illustrating an execution procedure of a drivinglimitation routine;

FIG. 3A to FIG. 3E each shows a timing chart illustrating an example ofa state in which a driving force limitation process is prohibited;

FIG. 4 is a graph illustrating a relationship between vehicleacceleration and reduction amount of a driving force by a driving forcelimitation process; and

FIG. 5 is a graph illustrating a relationship between vehicleacceleration, vehicle speed and a determination value in a driving forcelimitation process.

DETAILED DESCRIPTION OF EMBODIMENTS

A specific embodiment of the driving control system for a vehicleaccording to the invention is explained next. As illustrated in FIG. 1,an internal combustion engine 2 and an automatic transmission 3 areinstalled in a vehicle 1. The internal combustion engine 2 is a drivingsource and the automatic transmission 3 performs automatically a shiftoperation. The internal combustion engine 2 is connected to wheels 4 viathe automatic transmission 3. As a result, a driving force outputted bythe internal combustion engine 2 is transmitted to the wheels 4 via theautomatic transmission 3 and the like. The wheels 4 rotate as a result,thereby enabling travel of the vehicle 1. The automatic transmission 3is provided with a plurality of gears. The automatic transmission 3 isconfigured in such a manner that combinations of the plurality of gearscan be modified so as select, any one from among a plurality of gearpositions established beforehand. The automatic transmission 3 cantransmit the driving force outputted by the internal combustion engine 2to the wheels 4, and can interrupt transmission of the driving forceoutputted by the internal combustion engine 2.

A shift mechanism 5 for switching the operation mode of the automatictransmission 3 is mounted in the vehicle 1. The select lever 6 of theshift mechanism 5 is coupled to the automatic transmission 3(specifically, to the shift fork thereof). The select lever 6 isshifted, by the driver, to any one of a plurality of operation positionsthat include a parking position, a reverse travel (reverse) position, aneutral position and a forward travel (drive) position. The operationmode of the automatic transmission 3 for each operation position of theselect lever 6 will be explained further on.

When the select lever 6 is operated to the parking position, there isprohibited rotation of the wheels 4 through meshing of gears in theautomatic transmission 3, and a power interrupt state is brought aboutin which transmission of the driving force outputted by the internalcombustion engine 2 to the wheels 4 is interrupted.

When the select lever 6 is operated to the neutral position, theprohibiting of rotation of the wheels 4 through gear meshing in theautomatic transmission 3 is released, and a power interrupt state isbrought about in which transmission of the driving force outputted bythe internal combustion engine 2 to the wheels 4 is interrupted. Whenthe select lever 6 is operated to the drive position, a powertransmission state is brought about in which the driving force outputtedby the internal combustion engine 2 is transmitted to the wheels 4 in aforward rotation direction. The vehicle 1 is brought herein to a statein which the vehicle is capable of forward travel. When the select lever6 is operated to the reverse position, a power transmission state isbrought about in which the driving force outputted by the internalcombustion engine 2 is transmitted to the wheels 4 in a reverse rotationdirection. The vehicle 1 is brought herein to a state in which thevehicle is capable of reverse travel. In the present embodiment, theselect lever 6 functions as an operation unit.

An electronic control system 7 (controller) is installed in the vehicle1.

The electronic control system 7 executes various control relating to theinternal combustion engine 2 and the automatic transmission 3. Varioussensors are attached in the vehicle 1. The sensors are a vehicle speedsensor 8 for detecting the travel speed (vehicle speed SPD) of thevehicle 1, and an accelerator position sensor 10 for detecting anoperation amount (accelerator operation amount ACC) of an acceleratoroperation member 9 (accelerator pedal, accelerator lever or the like).In addition, there are provided, for instance, shift position sensors 11a, 11 b, 11 c, 11 d, attached on the shift mechanism 5, for detectingthe operation position (shift position SP) of the shift mechanism 5(specifically, the select lever 6). The shift position sensor 11 a is aswitch that is switched on when the select lever 6 approaches a parkingposition, and that is switched off when the select lever 6 moves awayfrom the parking position. The shift position sensor 11 b a switch thatis switched on when the select lever 6 approaches the reverse positionand that is switched off when the select lever 6 moves away from thereverse position. The shift position sensor 11 c is a switch that isswitched on when the select lever 6 approaches the neutral position andthat is switched off when the select lever 6 moves away from the neutralposition. The shift position sensor lid is a switch that is switched onwhen the select lever 6 approaches the drive position and that isswitched off when the select lever 6 moves away from the drive position.Output signals of the various sensors are input to the electroniccontrol system 7. For instance, a driving circuit for driving theinternal combustion engine 2 and a driving circuit for driving theautomatic transmission 3 are connected to the electronic control system7. In the present embodiment, the shift position sensors 11 a to 11 dfunction as detection units that are respectively attached for eachoperation position of the operation unit. The shift position sensors 11a to 11 d and the electronic control system 7 function as a positiondetection device that detects the operation position of the operationunit on the basis of an output signal of the detection unit.

The electronic control system 7 adjusts the driving force outputted bythe internal combustion engine 2 in accordance with, for instance, theaccelerator operation amount ACC. The electronic control system 7switches the gear position of the automatic transmission 3 on the basisof the accelerator operation amount ACC, the vehicle speed SPD and theshift position SP.

Upon start of the vehicle 1, the driver ordinarily shifts the operationposition of the select lever 6 from a non-driving position (parkingposition or neutral position) to a driving position (drive position orreverse position), and, thereafter, operates the accelerator operationmember 9, which is in an off-state, to an on-state. When the driver isin a hurry, the operation of bringing the accelerator operation member 9from the off-state to the on-state (hereafter also referred to as“on-operation”) is performed in some instances earlier than theoperation of shifting the select lever 6 from a non-driving position toa driving position. In such cases, the driver, even though intending toperform the above-described ordinary operation, performs actually anoperation that is different from the ordinary one, i.e. the drivershifts the select lever 6 from a non-driving position to a drivingposition in a state where the accelerator operation member 9 is operatedto the on state.

In such instances where the driver inadvertently performs an operationdifferent from an ordinary operation, a difference may arise between thebehavior of the vehicle 1 as envisaged by the driver and the actualbehavior of the vehicle 1. Specifically, the driver intends to thevehicle 1 to start when the accelerator operation member 9 ison-operated. In actuality, by contrast, the vehicle 1 starts throughtransmission of the driving force of the internal combustion engine 2 tothe wheels 4 upon shifting of the select lever 6 from a non-drivingposition to a driving position after the accelerator operation member 9is operated to the on state. Such a discrepancy with respect to thebehavior of the vehicle 1 causes discomfort to the driver, andconstitutes a factor that decreases the drivability of the vehicle 1.

In the present embodiment, a driving force limitation process thatsuppresses the driving force that is outputted by the internalcombustion engine 2, as compared with that during an ordinary operation,is executed when the select lever 6 is shifted from a non-drivingposition (parking position or neutral position) to a driving position(drive position or reverse position) in a state where the acceleratoroperation member 9 is operated to the on state. In consequence, theoperation unit is shifted from a non-driving position to a drivingposition in a state wherein driving force outputted by the motor isincreased when the accelerator operation member 9 is operated to the onstate. In other words, switching of transmission from a power interruptstate to a power transmission state is suppressed. The decrease indrivability caused by transmission of this driving force is thussuppressed.

In the system of the present embodiment, the above driving forcelimitation process is executed when the accelerator operation member 9is operated from an off-state to the on state before the operationposition of the select lever 6 is shifted from a non-driving position toa driving position, for instance when the driver attempts to start thevehicle 1 in a hurry. Thereby, the driving force that is outputted bythe internal combustion engine 2 is suppressed through execution of thedriving force limitation process, also in a case where the driver shiftsthe select lever 6 from a non-driving position to a driving position, ina state where the accelerator operation member 9 is operated to the onstate. As a result there is suppressed discomfort to the driver as thevehicle 1 begins traveling through transmission of the driving force tothe wheels 4.

In the position detection device of the present embodiment, theoperation position of the select lever 6 is detected on the basis of theoutput signals from the shift position sensors 11 a to 11 d that areattached to respective operation positions of the select lever 6. As aresult, the shift position sensors 11 a to 11 d are all brought to aturned-off state when, in the process of shifting the operation positionof the select lever 6, the select lever 6 is brought to an intermediateposition between operation positions (specifically, to an intermediateposition between two adjacent operation positions). Thus, a state isdetected wherein the select lever 6 is not operated to any of theoperation positions. The state in which the detection result by theposition detection device shows that the select lever 6 is not operatedto any of the operation positions is a temporary state. Nevertheless,such a state may persist for a comparatively long time, depending on theoperation mode of the select lever 6, in cases where, for instance, theoperation speed of the select lever 6 is low.

When the above state arises upon-operation of the select lever 6 from anon-driving position to a driving position, the operation state of theautomatic transmission 3 that is coupled to the select lever 6 isbrought to a power transmission state, and the operation position of theselect lever 6 as detected by the position detection devices is not adriving position. The vehicle 1 starts as a result of the actualoperation state of the automatic transmission 3 being brought to a powertransmission state, despite the fact that, at this time, the operationstate of the automatic transmission 3, as grasped on the basis of thedetection result by the position detection device, is still in a powerinterrupt state. As a result, the operation position of the select lever6 is brought thereafter to an adequate position, and the above-describeddriving force limitation process is initiated when the positiondetection device detects that the operation position of the select lever6 is at the driving position. Therefore, drivability may decreases,during travel of the vehicle 1, due to stalling of the vehicle 1.

In the system of the present embodiment, thus, a discrepancy may arisebetween the actual operation state of the automatic transmission 3 andthe operation state of the automatic transmission 3 as grasped by theposition detection device. Such a discrepancy may result in decreases ofdrivability.

The driving force limitation process in the system of the presentembodiment is prohibited when the below-described condition (1) andcondition (2) are both satisfied, even in a case where there issatisfied the execution condition of the driving force limitationprocess on the basis of which the select lever 6 is operated from anon-driving position (parking position or neutral position) to a drivingposition (drive position or reverse position), in a state where theaccelerator operation member 9 is operated to the on state. Condition(1) specifies that the vehicle 1 is traveling.

Specifically, a gear position other than the lowest-speed gear positionis set as the gear position of the automatic transmission 3. Condition(2) the state in which all the shift position sensors 11 a to 11 d areturned off is continued, for a predetermined period (for instance,several seconds) established beforehand, immediately before it isdetermined that the operation position of the select lever 6 has beenshifted from a non-driving position to a driving position.

In the system of the present embodiment a lowest-speed gear position, oflarge speed ration, is set as the gear position of the automatictransmission 3 upon stop of the vehicle 1. Thus, the higher the travelspeed of the vehicle 1, the higher the speed, of small speed ration, ofthe gear position to which the gear position the automatic transmission3 is changed, during forward travel of the vehicle 1. As a result, thespeed ration of the automatic transmission 3 becomes lower than apredetermined ratio. In other words, there is set, as the gear positionof the automatic transmission 3, a gear position other than thelowest-speed gear position; accordingly, it becomes possible todetermine, with good precision, that the vehicle 1 is traveling forward.Condition (1) is set in the present embodiment with the aboveconsideration in mind.

The above condition (1) is set in the present embodiment. Therefore, thedriving force limitation process is prohibited when it is determinedthat the vehicle 1 is travelling, even when it is determined that theoperation position has been shifted from a non-driving position to adriving position, on the basis of the operation position detected by theposition detection device, in a state where the accelerator operationmember 9 is operated to the on state. As a result, travel of the vehicle1 is initiated when the actual operation state of the automatictransmission 3 is firstly brought to the power transmission state,upon-operation of the select lever 6 from a non-driving position to adriving position. Thereafter, the limitation of the above driving forceby the driving force limitation process is not performed in a case whereit is determined that the operation position detected by the positiondetection device has been shifted to a driving position. Suddendecreases of the driving force outputted by the internal combustionengine 2 during travel of the vehicle 1 can be suppressed as a result.Stalling of the vehicle 1 caused by a decrease in the driving force isthus suppressed, and decreases in drivability can be accordinglysuppressed.

The above condition (2) is set in the present embodiment. Therefore, itbecomes possible to accurately grasp that the vehicle 1 is now in atravelling state as a result of the actual operation state of theautomatic transmission 3 being brought to a power transmission state,despite the fact that the operation state of the automatic transmission3, as determined on the basis of the detection result by the positiondetection device, remains in a power interrupt state, as describedabove. Decreases in drivability can thus be suppressed by prohibitingthe driving force limitation process on the basis of that determination.A period over which the vehicle 1 can be thus accurately determined tobe in a travelling state is worked out beforehand, on the basis ofexperimental or simulation results, and is stored in the electroniccontrol system 7, as the predetermined period of condition (2). In thepresent embodiment it is determined, from the fact that the abovecondition (2) is satisfied, that the operation unit is not operated toany of the operation positions on the basis of the detection result,immediately before it is determined that the operation position of theselect lever 6 has been shifted from a non-driving position to a drivingposition. Specifically, it is not determined that the operation unit isnot operated to any of the operation positions on the basis of thedetection result by the position detection device, immediately before itis determined that the operation state has been shifted from anon-driving position to a driving position in the case of a state whereall the shift position sensors 11 a to 11 d are turned off over a veryshort lapse of time accompanying the ordinary operation of the selectlever 6.

The execution procedure and effect of the driving limitation routinehaving the above driving force limitation process are explained indetail next with reference to the flowchart illustrated in FIG. 2A andFIG. 2B. For instance, the series of processes illustrated in theflowchart are executed periodically, with interruptions, at interspersedlapses of time, by the electronic control system 7.

In the routine, firstly, an execution flag is set to an off state, asillustrated in FIG. 2 A and FIG. 2B (S101). The execution flag is offsetto an on state when the driving force limitation process (S107). On theother hand, the execution flag is set to an off state when the drivingforce limitation process is stopped. In the process of S101, it isdetermined, on the basis of the operation state of the execution flag,whether the driving force limitation process is stopped or not.

If the execution flag is set to an off state (S101: YES), it isconsidered that the driving force limitation process is not beingexecuted, and it is determined whether or not a state has been broughtabout (specific state) wherein the select lever 6 is shifted from anon-driving position to a driving position, in a state where theaccelerator operation member 9 is operated to the on state (S102 andS103). Specifically, it is determined whether condition (3) andcondition (4) below are both satisfied. Condition (3): the acceleratoroperation member 9 is on-operated. Specifically, the acceleratoroperation amount ACC is greater than a predetermined value. Condition(4): regarding the operation position of the shift mechanism 5 asgrasped on the basis of the detection result by the position detectiondevice, the operation position at a time of a previous execution of thepresent routine is a non-driving position and the operation positionupon current execution of the present routine is a driving position.

When either condition (3) or condition (4) is not satisfied (S102: NO orS103: NO), the above specific state does not hold, and the presentroutine is temporarily terminated without execution of subsequentprocessing.

On the other hand, when condition (3) and condition (4) are bothsatisfied thereafter through repeated execution of the present routine(S102: YES and S103: YES), it is considered that the specific stateholds, and it is determined next whether or not the abovementionedcondition (1) and condition (2) are satisfied (S104 and S105).

If condition (1) and condition (2) are both satisfied (S104: YES andS105: YES), the present routine is temporarily terminated withoutexecution of subsequent processing. At this time, it is considered thatthere is a possibility of decrease in drivability caused, as describedabove, by a discrepancy between the actual operation state of theautomatic transmission 3 and the operation state of the automatictransmission 3 as grasped on the basis of the detection result by theposition detection device, and the driving force limitation process isprohibited.

If either condition (1) or condition (2) is not satisfied (S104: NO orS105: NO), it is considered that there is a low likelihood ofdrivability decreasing on account of the abovementioned offset, theexecution flag is set to an on state (S106) and the driving forcelimitation process is initiated (S107). The execution procedure of thedriving force limitation process will be explained in detail further on.Thereafter, the driving force limitation process is continued, unlessthe above execution flag is set to an off state (S101: NO).

A process (process from S108 to S110) relating to termination of thedriving force limitation process is executed during execution of thedriving force limitation process (S101: NO or S104: NO or S105: NO).Specifically, it is firstly determined whether condition (5) below issatisfied or not (S108). In condition (5), the driving force is adriving force that is to be outputted by the internal combustion engine2 in accordance with the accelerator operation amount ACC, but issmaller than a controlled driving force, which is the driving forceafter being suppressed in the driving force limitation process, forinstance when the accelerator operation amount ACC becomes “0” throughthe accelerator operation member 9 is released by the driver.

If condition (5) is not satisfied (S108: NO), the driving forcelimitation process is continued, without stops (process of S109 and S110is skipped). Thereafter, if the abovementioned condition (5) issatisfied through repeated execution of the routine (S108: YES), thedriving force limitation process is stopped (S109), and the executionflag is set to an off state (S110), after which the present routine istemporarily terminated. Limiting of the driving force that is outputtedby the internal combustion engine 2 is stopped thereafter. Thus, thedriving force is adjusted so as to match the requested driving forcethat is a driving force that should be out put form the internalcombustion engine 2 on the basis of the accelerator operation amountACC, so as to match the requested driving force.

In the driving limitation routine of the present embodiment, the drivingforce limitation process is not executed when the abovementionedcondition (1) and condition (2) are both satisfied even in a case wherethe select lever 6 is operated from a non-driving position to a drivingposition, in a state where the accelerator operation member 9 isoperated to the on state. Herein, it becomes possible to accuratelygrasp that the vehicle 1 is now in a travelling state as a result of theactual operation state of the automatic transmission 3 being brought toa power transmission state, despite the fact that the Operation state ofthe automatic transmission 3, as grasped on the basis of the detectionresult by the position detection device, remains in a power interruptstate. It becomes possible to suppress sudden decreases thereafter inthe driving force accompanying the detection, by the position detectiondevice, of the operation to the driving position.

FIG. 3 illustrates an example of a state in which the driving forcelimitation process is prohibited. In the example illustrated in FIG. 3,the select lever 6 is at a position intermediate between the neutralposition and the drive position (time t1 to t3) in a process of shiftingto the drive position from a state in which the select lever 6 isoperated to the neutral position (until t1).

A state is brought about in which all the shift position sensors 11 a to11 d are turned off, including the shift position sensor 11 c (FIG. 3C)and 11 d (FIG. 3D). As a result, a state is detected, by the positiondetection device, in which the select lever 6 is not operated to any ofthe operation positions. In the present embodiment, vehicle control isexecuted then on the basis of the operation position (FIG. 3E) of theselect lever 6 as detected immediately before the state in which theselect lever 6 is not operated to any of the operation positions.

In the sate in the select lever 6 is not operated to any of theoperation positions, the vehicle 1 starts if the actual operation state(actual operation state, FIG. 3B) of the automatic transmission 3 thatis coupled to the select lever 6 is operated to a drive position.Meanwhile the operation state (hereafter also referred to as “controloperation state”, FIG. 3E) of the automatic transmission 3 as determinedon the basis of the operation position of the select lever 6, asdetected by the position detection device, remains at the neutralposition. In the present example, the accelerator operation member 9(FIG. 3A) is on-operated at time t2. As a result, the output of theinternal combustion engine 2 increases thereafter, the vehicle 1accelerates thereby, and the gear position of the automatic transmission3 is shifted to a high-speed gear position.

Thereafter, at time t3, the shift position sensor 11 d is turned on inthat, for instance, the select lever 6 is operated to an adequateposition. Thereupon, an operation state is brought about of the time atwhich the control operation state is operated to a drive position.Accordingly, the abovementioned condition (3) and condition (4) are bothsatisfied. If the driving force limitation process is hypotheticallyinitiated at that time, the driving force outputted by the internalcombustion engine 2 decreases despite the fact that the vehicle 1 istraveling at a comparatively high speed by the accelerator operationmember 9 being operated to the on state. The vehicle 1 stalls as aresult, and drivability decreases.

In the system of the present embodiment, the driving force limitationprocess is not initiated when the abovementioned condition (1) andcondition (2) are both satisfied, even if condition (3) and condition(4), which are execution conditions of the driving force limitationprocess, are both satisfied. Specifically, the driving force limitationprocess is prohibited in a case where a state in which the shiftposition sensors 11 a to 11 d are all turned off continues for apredetermined period, established beforehand, immediately before it isdetermined that the vehicle 1 is traveling and that the operationposition of the select lever 6 has been shifted from a non-drivingposition to a driving position. As a result, there is suppressedinitiation of the driving force limitation process during travel(specifically, at time t3) of the vehicle 1. Decreases in drivabilityare accordingly suppressed by suppressing the stalling of vehicle 1.

A limitation mode of the driving force in the driving force limitationprocess (process of S107 in FIG. 2B) will be explained next in detailwith reference to FIG. 4 and FIG. 5. In the driving force limitationprocess, suppression of the driving force that is outputted by theinternal combustion engine 2 is realized by reducing the driving forceby a reduction amount. Accordingly, the greater the above reductionamount is, the greater becomes the degree of suppression of the drivingforce by the driving force limitation process. The degree of suppressionof the driving force is modified in accordance with the acceleration(vehicle acceleration D) in the advance direction of the vehicle 1,determined on the basis of a detection signal of the vehicle speedsensor 8. For instance, the greater the vehicle acceleration D, thegreater the reduction amount is and the greater becomes the degree ofsuppression of the driving force that is outputted by the internalcombustion engine 2. More specifically, for instance, when the vehicleacceleration D is smaller than a determination value HA, the abovereduction amount is set to “0” and the degree of suppression of theabove driving force is set to “0”, as illustrated in FIG. 4. On theother hand, when the vehicle acceleration D is equal to or greater thanthe determination value HA, the greater the vehicle acceleration Dbecomes, as compared with the determination value HA, the greaterbecomes the increase of the above reduction amount with respect to “0”,and the greater becomes the increase, with respect to “0”, of the degreeof suppression of the driving force that is outputted by the internalcombustion engine 2.

Executing the driving force limitation process as described aboveobtains the effect of suppressing the driving force that is outputted bythe internal combustion engine 2 so as not to cause discomfort to thedriver, while avoiding useless suppression of the driving force. Insituations such as those where the vehicle 1 is getting out of a muddyroad, the driver repeatedly shifts in some instances the select lever 6between a non-driving position and a driving position. In such cases theselect lever 6 may sometimes be shifted from a non-driving position tothe reverse position, in a state where the accelerator operation member9 is operated to the on state. Thus, the vehicle acceleration D does notincrease easily even if the select lever 6 is shifted from a non-drivingposition to the reverse position, in a state where the acceleratoroperation member 9 is operated to the on state, when the driver attemptsto get the vehicle 1 out of a muddy road. As a result, the degree ofsuppression of the above driving force through the driving forcelimitation process becomes smaller. Accordingly, it becomes possible tosuppress the hindrance that suppression of the driving force by thedriving force limitation process poses to getting the vehicle 1 out ofthe muddy road. The drivability of the vehicle 1 is therefore enhanced,for example, in instances where the vehicle 1 to move off a muddy road.

The determination value HA that is used in the driving force limitationprocess is variably set so as to become an optimal value that isestablished beforehand on the basis of experimentation or the like, inaccordance with the vehicle speed SPD. The determination value HAchanges in response to the vehicle speed SPD, for instance as denoted bythe solid line in FIG. 5. As FIG. 5 shows, the determination value HA isset to be a constant optimal value established beforehand throughexperimentation or the like, when the vehicle speed SPD is smaller thana predetermined speed KB. When the vehicle speed SPD is equal to orgreater than the predetermined speed KB and smaller than the referencespeed KA, the determination value HA decreases gradually accompanying arise in the vehicle speed SPD. When the vehicle speed SPD is equal to orgreater than the reference speed KA, the determination value HA is “0”.Therefore, when the vehicle speed SPD is equal to or greater than thereference speed KA upon execution of the driving force limitationprocess, the degree of suppression of the driving force outputted by theinternal combustion engine 2 becomes greater than “0”, in accordancewith the vehicle acceleration D, regardless of the magnituderelationship between the vehicle acceleration D and the determinationvalue HA. That is, the above reduction amount is set to a value greaterthan “0”, in accordance with the vehicle acceleration D, so as to renderthe degree of suppression of driving force outputted by the internalcombustion engine 2 to be greater than “0”, as described above. In thiscase, discomfort to the driver can be suppressed by accuratelysuppressing the above driving force when the vehicle speed SPD isgreater than the reference speed KA, i.e. when the driver is likely tofeel the abovementioned discomfort upon execution of the driving forcelimitation process.

As explained above, the present embodiment obtains the followingeffects. 1. The driving force limitation process is prohibited when astate in which all the shift position sensors 11 a to 11 d are turnedoff continues for a predetermined period immediately before it isdetermined that the vehicle 1 is traveling and that the operationposition of the select lever 6 has been shifted from a non-drivingposition to a driving position, even when a non-driving position isdetermined to have been shifted to a driving position on the basis ofthe operation position detected by the position detection device, in astate where the accelerator operation member 9 is operated to the onstate. As a result, it becomes possible to suppress stalling of thevehicle 1 that is caused by sudden decreases of the driving forceoutputted by the internal combustion engine 2 during travel of thevehicle 1. Decreases in drivability can be suppressed as a result.

2. It becomes possible to determine, with good precision, that thevehicle 1 is traveling from the fact that a gear position other than alowest-speed gear position is set to the gear position of the automatictransmission 3. The above embodiment may accommodate the followingvariations.

The shift position sensors 11 a to 11 d are not limited to proximityswitches. Any sensors may be used, for instance proximity sensors,provided that the sensors output dissimilar signals when the selectlever 6 approaches the operation position, that is to be detected, andwhen the select lever 6 moves away from that operation position.

The way in which the driving force limitation process is executed can bemodified arbitrarily, so long as it is possible to limit the drivingforce outputted by the internal combustion engine 2. For instance, thedetermination value HA may be set to be constant, irrespective of thevehicle speed SPD. The degree of limitation of the driving force that isoutputted by the internal combustion engine 2 may be modified inaccordance with the driving state of the vehicle 1, other than thevehicle acceleration D, for instance by being set to vary in accordancewith the vehicle speed SPD alone, or in accordance with the acceleratoroperation amount ACC.

As the condition for determining that the vehicle 1 is traveling therecan be set any condition, for instance condition (6) or condition (7)below, instead of the abovementioned condition (1). In condition (6),the vehicle speed SPD is equal to or greater than a predetermined speed.In condition (7), the vehicle acceleration D is greater than apredetermined value, and the driving force outputted by the internalcombustion engine 2 is greater than a predetermined value.

As the operation member of the shift mechanism that is shifted by thedriver and that is coupled to the automatic transmission there can beused a member other than a select lever, for instance a member that isoperated by a switching button or by sound.

The invention is not limited to a vehicle having installed therein amultistage automatic transmission having a plurality of gear positions,and can be used also in a vehicle in which there is installed acontinuously-variable automatic transmission such that a speed ration ismodified in a stepless manner. In a case where the driving controlsystem according to the above-described embodiment is used in a vehiclein which such a continuously variable automatic transmission isinstalled, it is sufficient to determine that the vehicle is travelingon the basis of the speed ration of the automatic transmission asgrasped by an electronic control system, for instance through setting ofcondition (8) below, instead of condition (1). Condition (8): the speedration of the automatic transmission as grasped by the electroniccontrol system is smaller than a predetermined ratio.

The invention is not limited to a vehicle in which an internalcombustion engine is installed as a driving source, and can be used inany vehicle so long as the vehicle has a motor as a driving source andinstalled therein, for instance a vehicle in which an electric motor isinstalled as a driving source, or a vehicle in which an internalcombustion engine and an electric motor are installed as drivingsources.

While the disclosure has been explained in conjunction with specificexemplary embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, exemplary embodiments of the disclosure as set forthherein are intended to be illustrative, not limiting. There are changesthat may be made without departing from the scope of the disclosure.

What is claimed is:
 1. A driving control system for a vehicle,comprising: a shift mechanism that is used in a vehicle in which a motoras a driving source is coupled to wheels via a transmission, and that isconfigured such that an operation unit coupled to the transmission isselectively shifted to one operating position of a driving position anda non-driving position; a position detection device that detects theoperation position of the operation unit on the basis of an outputsignal of a detection unit that is attached to each of the operationpositions of the operation unit; and a controller that executes adriving force limitation process for limiting a driving force that isoutputted from the motor, when it is determined that the operating unitis shifted from the non-driving position to the driving position on thebasis of the operation position of the operation unit detected by theposition detection device, in a state that the accelerator operationmember of the vehicle is operated to an on state; wherein the shiftmechanism brings the transmission to a power transmission state in whichthe driving force from the motor is transmitted to the wheels, when theoperation unit is operated to the driving position, and brings thetransmission to a power interrupt state in which transmission of thedriving force from the motor to the wheels is interrupt, when theoperation unit is operated to the non-driving position; and thecontroller prohibits the driving force limitation process when it isdetermined that the vehicle is traveling and that the operation unit isnot operated to any of the operation positions on the basis of adetection result by the position detection device.
 2. The drivingcontrol system for a vehicle according to claim 1, wherein thecontroller makes the determination that the operation unit is notoperated to any of the operation positions on the basis of the detectionresult by the position detection device immediately before it isdetermined that the non-driving position has been shifted to the drivingposition.
 3. The driving control system for a vehicle according to claim1, wherein the controller determines that the vehicle is traveling whena speed ratio of the transmission is smaller than a predetermined ratio.4. The driving control system for a vehicle according to claim 1,wherein the detection unit is a switch that is attached to each of theoperation positions to be detected by the detection unit, and that isoperated to an on state when the operation unit approaches the detectionunit, and is operated to an off state when the operation unit moves awayfrom the operation position.